Enceladus, second nearest of the major regular moons of Saturn and the brightest of all its moons. It was discovered in 1789 by the English astronomer William Herschel and named for one of the Giants (Gigantes) of Greek mythology.
Enceladus measures about 500 km (310 miles) in diameter and orbits Saturn in a prograde, nearly circular path at a mean distance of 238,020 km (147,899 miles). Its average density is only 60 percent greater than that of water, which indicates that its interior contains appreciable amounts of non-ice material. Its surface, which reflects essentially all of the light that strikes it (compared with about 7 percent for Earth’s Moon), is basically smooth but includes cratered and grooved plains. The surface is almost pure water ice, with trace amounts of carbon dioxide, ammonia, and light hydrocarbons.
Enceladus’s current activity is responsible for Saturn’s E ring, a tenuous ring of micrometre-sized particles of water ice condensed from vapour ejected by the geysers. The particles are densest near Enceladus’s orbit and are analogous to the cloud of orbiting particles ejected from Jupiter’s volcanically active moon Io. The E ring, however, appears to be much more extensive, reaching out to the orbit of Rhea and perhaps beyond. The orbital lifetimes of the E ring particles are very short, perhaps only 10,000 years, but they are resupplied continually by cryovolcanic eruptions. The E ring coats Enceladus and the other major inner moons of Saturn to give them a bright appearance.
Credit : Britannica
Picture Credit : Google
